Timeline

Origin and history

Mount Gerbier-de-Jonc is a phonolitic dome formed 8 million years ago by a viscous lava extrusion, typical of the pelean volcano. Located in the mountains of Vivarais (Central Massif), it is part of the Mézenc massif and marks the dividing line of the waters between Atlantic and Mediterranean. His name, of poorly understood pre-celtic origin, was recomposed into "Gerbier de Jonc", although he had no connection with rushes or gerbers. The top, prismed and eroded by the glaciations, is surrounded by scoops resulting from the fragmentation of its phonolite rich in sanidine and daugite crystals.

Rainwater infiltrates its prisms and traverses cracked basalts before feeding a groundwater table into a granitic arena. This table gives birth to the three sources of the Loire, the longest river in France, located at its foot. These sources, whose name is sometimes disputed, make the Gerbier-de-Jonc a symbolic place, celebrated each year during the "circle of the three sources", bringing together representatives of villages where other major European rivers, such as the Danube, are born.

Ranked a natural site since 1933 and ZNIEFF type I zone (280 hectares), the mountain is home to protected species and attracts more than 400,000 annual visitors, mainly local. Its free ascent (30 minutes) and its recent developments, such as the house of the site opened in 2017 (former chalet-hotel transformed), make it the second tourist site of the Ardèche. The department invested 4.5 million euros in 2016 to preserve this heritage, while valuing local traditions such as the "Fine Fats Beef of Mezenc" (AOC), celebrated every Easter Monday.

The Gerbier-de-Jonc is also a place of passage for sporting events, such as the Ardéchoise, a cyclosportive whose route "La Volcanique" (176 km) crosses the adjacent pass (1,417 m) each June. Its geological history, linked to the alpine orogenesis and fracturations of the hercynian base, makes it a witness to the ancient volcanic activities of the eastern Velay, between 13 and 7 million years. Today, it embodies both a major natural, cultural and tourist heritage in Auvergne-Rhône-Alpes.

Its scientific name, suc, designates in the region volcanic reliefs with characteristic shapes. The site, managed by the Ardèche department, also illustrates the challenges of preserving sensitive natural areas, with remarkable fauna and flora, protected for nearly a century.

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